A fluorometer including an array of light-emitting diode (LED) light sources in one-to-one correspondence with sample containers is described in International Publication No. WO 01/35079, which is incorporated herein in its entirety by reference. Various problems can be encountered, however, with such a system. For example, such a system can be costly for commonly used experimentation involving analysis of a 96 sample well array and would require 96 LED light sources. The use of one light source per well, can also result in photo-bleaching of fluorescent dyes present in samples being analyzed